Biting the Big Apple
by DragonKnight159
Summary: (On hiatus) What should have been a relaxing day for Castle and Beckett turns into a much bigger crime than they could have imagined when two "FBI" agents show up for an unusual crime. Set Castle Season 5 and Supernatural Season 8. Contains Caskett.
1. Catching a Case

_There are two kinds of folks who sit around thinking about how to kill people: Psychopaths and mystery writers. I'm the kind that pays better. Who am I? I'm Rick Castle. Every writer needs inspiration and I've found mine. And thanks to my friendship with the Mayor I get to be on her case. And together we catch killers._

* * *

Richard Castle sat in his office, reading through some Nikki Heat fanfic that he'd discovered. The only reason this story had caught his attention was because it involved vampires. He knew better than to think that vampires existed but all the same he was kind of wishing he had written it first.

"Hey, Dad," Alexis said as she came down the steps. "What are you doing up so early?"

"Started reading something last night and came down to finish it," Castle replied without taking his eyes off the screen. "Which reminds me, have you seen your grandmother anywhere this morning?"

"No. I don't remember her ever actually coming home last night," Alexis answered as she poured herself a glass of orange juice. "Things must be going well with that guy she met at her acting studio." Castle muttered something incoherent. He had no wish to get involved in his mother's personal life, so long as the guy didn't try stealing her money. "Where's Beckett?"

"Oh she's doing stuff down at the precinct," Castle said as he finished the chapter he was on and closed his laptop. "We were thinking of having a relaxing day to ourselves but she has a bunch of paperwork to do that Captain Gates has been giving her a hard time about."

"Are you going to that new restaurant on 53rd?"

"That was the plan." Castle stood up and took the juice his daughter offered him. "How 'bout you?"

"I was going to get together with some friends, you know, blow off some steam before midterms," Alexis said, sitting down to her bowl of cereal. She was going to continue when Castle's phone started ringing, prompting her father to answer it.

"Why hello, Beckett. Alexis and I were just talking about you," he said with a smile that quickly disappeared. "What? Seriously? Alright just let me get dressed and I'll meet you there." He hung up and set the phone on the counter.

"Murder?" Alexis asked with a smirk and her father sighed.

"On the bright side we do get to spend the day together," he said with a shrug.

It didn't take him long to change and grab a cab to Central Park where Beckett was waiting for him. "Took you long enough," she said as she handed him a coffee cup, much to his surprise.

"But I always get _you_ coffee," Castle said dumbfounded.

"What? I can't change things up once and a while?" she asked with a laugh. "Laney's already at the scene. White male, mid 30s, beat cop called it in."

"Any cause of death yet?"

"She should have it by the time we get there." After several minutes of walking they came upon Laney in a ditch hunched over a body. "Homeless?"

"You'd think so but no," Laney answered standing up. "Someone dressed him and then positioned him like he was sleeping. Whoever did this thought it through. That's not the weird part though." She rolled up his sleeve revealing a series of bite marks.

"Someone got an early breakfast," Castle commented. "Any idea on the animal?"

"None that I've ever seen," Laney said, rolling the sleeve back down. "So far I've found bites on all of his limbs and his neck."

"What could have done this?" Beckett asked baffled.

"Makeout session gone horribly, horribly wrong," Castled answered before Laney could. "Or right depending on what you're into."

"No idea on the bites," Laney said, "but based on lividity and liver temp I put time of death between midnight and three. I'll know more once we get him back to the morgue." She nodded to her staff who then loaded the body on a gurney and carted him off to the van. At that point two men dressed in black suits walked up the crime scene, flashing badges at the police line and crossing under it. The taller of the two had longer brown hair and a gentler air about him while the shorter one's brown hair was cut short. He seemed to walk with a bit of a swagger that his partner lacked.

"I'm Special Agent Young," the short one said as Beckett and Castle met the halfway. "This is my partner, Special Agent Richards. We're with the FBI. I hear you found a body this morning."

"Detective Kate Beckett, Richard Castle," Beckett said, flashing her own badge and then nodding toward Castle. "Why is the FBI getting involved in a murder?"

"We think that this murder has something to do with others that we picked up on further north," Agent Richards answered. "I know the FBI has a reputation for taking over a case at this point but we'd like to work with you to catch whoever's doing this."

"That's a change," Castle said, turning to Beckett. "The FBI deferring to the NYPD."

"Yeah well it's not my call," Beckett said. "You're more than welcome to come down to the 12th Precinct and discuss with my Captain." The agents nodded and turned to talk to each other while Castle and Beckett went back to her cruiser.

"You really think this might be a vamp attack?" Dean Winchester asked his brother once he was sure that cop was out of earshot.

"Garth was pretty sure that the nest was coming to the city," Sam Winchester replied. "Besides, the cops here have got pretty good motivation to catch these guys."

"How about that detective?" Dean asked with a grin, turning to see Beckett still walking away.

"I'm pretty sure she's with him," Sam pointed out, referring to Castle. "Wait, did she say that was Richard Castle?"

"Pretty sure, why?"

"THE Richard Castle? As in the author with over twenty bestsellers and works with the NYPD to help solve murders?" Dean stared at his brother, oblivious to any of what he was saying.

"Did you just have a nerdgasm or something?" he asked after a moment. "How the hell should I know? C'mon, we should follow them back to the station." The brothers then headed off, getting in the Impala and driving off towards downtown New York.


	2. Teaming Up

**Author's Note: Sorry about the delay. I wasn't sure where I wanted this to head and after rewriting it twice finally came up with something I liked. The pace should pick up within the next chapter or so. Enjoy and thanks for the feedback thus far!**

* * *

"Special Agents Richards and Young I take it?" Capt. Victoria Gates asked the brothers as they stepped into her office.

"Yes, ma'am," Sam said.

"My mother is a ma'am. Captain will do just fine for me," Gates replied, slightly amused as they two men seemed to flinch. "Detective Beckett tells me you two want in on her case. Something about finding a similar case up north."

"Since our jurisdiction is the entire United States we have that right," Dean said with confidence. "But as Agent Richards told Det. Beckett we don't want to take over her case. We only _think_ the cases are related. Until we have evidence that they are it's her investigation and all we ask is to be kept in the loop until such time that we can verify that it's tied to our case."

"And then?"

"We bring the sicko that's doing this in together," Dean answered. "We have some leads we're going to work on until we find that the two intersect so we won't be in your hair." He turned to glance at Castle. "Seems you already have your hands full."

"Tell me about it," Gates muttered with a smirk. "Is there anyone at the bureau that can verify all this?"

"Of course," Sam said and pulled a business card from the inside of his jacket. "We'll head back to our office and let you know if we find anything."

"Appreciated." As they left the captain's office Sam let out a large sigh.

"That went well," he said as the brothers walked to the elevator.

"I can't believe I'm saying this but I think I'd rather deal with Crowley than her," Dean pointed out. "You think she made us?"

"Well if she did hopefully Garth throws her off long enough for us to get out of the city," Sam said as the doors opened. "Honestly I'm not even sure if this one of ours. We should probably check out the body before we get involved in a regular murder case."

"Great. Just great," Dean said as the elevator started down. "Dead bodies and people who hang out with dead bodies. Just my kind of day."

As they entered the morgue they saw Castle and Beckett standing with Lanie over the covered body. Dean had been expecting some crotchety smartass old man not a young hot woman. "This day just got better," he said quietly to Sam who just rolled his eyes. "And you are...?"

"I'm the ME, Lanie," Lanie replied with a coy smile. "You must be Agent Young and I have to say, not bad yourself."

"Time and a place you two," Beckett said. "I take it you're here to see the body."

"We want to make sure that we even have a link to your case," Sam answered. "We'd hate to be in your hair any longer than necessary."

"Well maybe you two can tell me what these are," Lanie said, pulling back the sheet to the body's waist. "If I didn't know better I'd say these look like-"

"Bite marks," Sam finished. "They look like bite marks from something with a mouth about the same shape and size as a human's, right?" Surprised, Lanie nodded as Sam and Dean looked at each other. "It's the same MO as up north."

"Meaning you're taking over," Castle stated.

"No. This is your turf and we'll follow your lead," Dean answered much to their surprise. "We're gonna head back to our place, see what we can find from the evidence we've collected so far."

"We'll do the same here and let you know if anything new comes up," Beckett offered as the two walked out. Once they were out of earshot she said, "Okay, anyone else not buying that they're FBI?"

"Are you kidding? I know a fake badge when I see one," Castle said. "Still, they act the part. And Capt. Gates seems to think they're legit."

"Despite all that, they were right on about these being bite marks," Lanie said. "So unless one of them has about six pairs of dentures with these kind of teeth I'd look elsewhere for your murderer." As Beckett and Castle walked out she yelled, "And give the cute one my number!"

The moment Sam and Dean got back to their motel they began calling their contacts. Dean went through list before settling on one he hadn't dialed for some time. The other line picked up after only two rings. "Now this is a number I thought I'd never see again."

"Good to hear from you two, Benny," Dean replied. "Listen, I know we didn't exactly leave things all that great but I was wondering if you'd heard anything."

"Depends on what," Benny replied. "This have anything to do with that business in Vermont?"

"Yeah and now it's in New York," Dean said. "You hear anything about a nest in this area?"

"Nest, no. But I have heard some rumblings from the underworld about this new group taking out other monsters."

"Like a turf war?"

"Yep. And whoever is leading this little gang has been recruiting," Benny added. "They've put out calls for vamps and shifters mostly."

"Thanks man," Dean said. "You take care of yourself." Benny echoed the sentiment before hanging up. Dean turned to Sam. "Hit gold."

"I thought you cut off all contact with him," his brother said.

"I'm not running off to help him," Dean replied. "Besides, he just gave us a huge clue: Something's putting the call out to vamps and shifters and telling others to get off its turf. Like it's raising an army."

"The last thing to do something like that was Dick Roman," Sam pointed out. "Besides, they just used the others out there, they didn't team up."

"It wouldn't be the first new thing that we've seen," Dean replied as he sat in front of the laptop. "If they want shifters then we might be able to see where they've keeping them." As if on cue Dean's phone rang as Beckett's number flashed on the screen. "This is Agent Young," he said. "Yeah we just got something actually. Really? Alright, we'll meet you there." He hung up.

"Well?" Sam asked.

"Their canvas turned up an alley where the vic was snatched from," Dean said. "The best part? It had security cameras so we might get an ID on who the shifters are using."

"Which might lead us to his apartment, therefore framing him," Sam finished.

"Who knows? We might get really lucky." Dean said as they locked the motel door and headed back into the city.


	3. The First Lead

**Author's Note: A quick correction. This is Supernatural Season _8_, not 7. Kudos to 'everythingwillbeperfect' for catching it.**

* * *

Castle and Beckett watched as the Winchesters pulled up in their car and get out. Despite her suspicions Capt. Gates had said the two of them were, in fact, with the Bureau after she'd talked with their boss Garth. The man was a bit off but all the information was there. Still, why would real agents need fake badges?

"Glad you two could join us," she said as they walked down the alley. "You never did say what the evidence you found was."

"Not so much evidence as information," Sam told her. "We have a...friend who keeps an eye out for weird crimes and he's been looking into places we can't go. From what he says there is something here in the city that's chasing out any competition and that they're looking for recruits."

"Specifically people who are good at blending in," Dean added. It wasn't the truth but then again it wasn't a complete lie. "The term this group uses is 'shifter' and the ones responsible for bleeding the victims-"

"Let me guess: vampires," Castle interrupted and Sam couldn't help but laugh.

"Vamps," Dean corrected him.

"So why would 'shifters' and 'vamps' be working together?" Beckett asked.

"Making the world a safer place for monsters to live in?" Sam sarcastically suggested. "Who knows how these psychos think?" As Beckett and Sam walked ahead Dean turned to Castle.

"So are you two, like..." he started, trying to lead Castle.

"Oh, us? It's, well, complicated," Castle answered, not sure how much to tell him. "She's not really up for seeing anyone right now."

"Not really what I was talking about but that's cool," Dean chuckled. "So how 'bout you? If she's the cool logical one that must make you either the comic relief or the brilliant sidekick that solves the majority of her cases."

"I'm just a writer who occasionally helps them have a breakthrough," Castle admitted. "Just don't tell Beckett I said that. She'd wonder why I'm not playing it up, saying I've helped her solve every case the last few years we've been partnered."

"So you believe in the unexplained, the supernatural?"

"You mean like vampires and shapeshifters?" Castle replied and Dean nodded. "I'm...willing to accept that there are some things in this world that I will never be able to explain. Turn them into a book, maybe. But to believe that they're real? And, anyway, since when do vampires have teeth like the bite marks we saw on the dead guy?"

"Just a question, dude," Dean said with a laugh. He was about to continue when he heard flapping wings just behind him and knew what was coming.

"You called for me, Dean?" a gravelly voice said. The four of them turned around to see Castiel in his usual attire.

"Cas?" Sam asked. "Why are you here?"

"One of you prayed for me and I came. It sounded urgent," the angel replied. Dean and Sam walked him toward the entrance of the alley where they talked in hushed tones for several minutes.

"Did you see him follow us here?" Beckett asked.

"No," Castle answered. "It's like he just _appeared_. What do you think he meant by 'pray'?"

"One way to find out," she said with a smirk as they walked up them. "Excuse me, sir. Is there a reason you followed us? You do realize that these two agents are working with us to solve a murder."

"It was an honest mistake," Castiel assured her, repeating what the boys had told him. "I'm their source for the information they gave you. I...received a call from someone in distress in this area and decided to find the agents so they could help me find him."

"And just how did this man call you?"

"I'm an Angel of the Lord. I can hear all prayers at any given time if I wished it." Beckett was about to say something when she saw Dean drawing circles around his temple.

"Right," Beckett said with a tight-lipped smile. She glanced over at Castle who just shrugged. Since the Winchesters seemed to have him under control they continued to the office where the security tapes were. The owner, a short balding fat man who seemed to be constantly sweating, let them in no questions asked. The started through the tapes and after almost an hour...

"What the hell?" Castle asked, rewinding his tape and replaying the scene a few times. "Beckett, you might wanna take a look at this." Beckett, Sam and Dean watched over his shoulder as a lone man walked into the alley, looked around, and then left.

"Why Castle, I believe you just solved the case for us," Beckett said sarcastically.

"Can you go back a few frames?" Sam asked. Castle did it and paused when Sam asked. "Look familiar, Agent Young?" The man was facing the camera and his eyes glowed as Dean swore under his breath.

"It's just a light reflection," Beckett explained. "This isn't a clue, it's a coincidence."

"There is no such thing as coincidence, Det. Beckett," Castiel said before staring at the image. "This must be one of the shapeshifters." He cocked his head and then closed his eyes and for a brief moment Beckett swore she could hear voices in the room with them. "His name is Michael Stofferson and he lives at 31 Canal St. Apt. 304."

"That's not too far from here," Castle said as he bagged the tapes for evidence.

"We are not going on a wild goose hunt just because he gave us the name of one guy and a random address," Beckett stated. "If anything I should arrest him for interfering in the investigation."

"If we check it out and there's nothing there then he's all yours," Dean offered her. "But what if we ignore it and it turns out to be something?"

"He's a got a point, Beckett," Castle added.

"I'm surrounded by idiots," she muttered, shaking her head. "Fine. We'll check this place out." They left the office and headed to their respective cars. As they made the short drive to the street Beckett turned to Castle. "You don't actually believe we're going to find anything, do you?"

"He is an Angel of the Lord," he pointed out, a smirk plastered on his face. "Someone prayed to him for help so we know it _has_ to be legitimate."

"What's more likely is that he's in on it. That's why he knows all these details."

"Then that would mean the feds are too," Castle realized, turning in his seat to face her. "Why else have the fake badges? And couldn't they have rerouted the captain's call to one of their friends who's posing as their boss?" He sat back down, barely containing his excitement. "Why didn't I ever think of this?"

"Because you're a better writer than that," she stated and he gave a grunt of approval. As she pulled into the parking garage of 31 Canal St. she said, "Alright, time to see just what the hell is going on." As they stepped out the Impala pulled up behind them and the three of them got out.

"How do you drive in this crap?" Dean asked as he checked his weapon.

"Helps to have a siren," Beckett pointed out as they entered the stairwell headed up to the lobby. They flashed their badges and the manager let them pass on their way to the third floor. When they reached Room 304 Beckett moved to one side while Sam and Dean took the other. She knocked on the door before saying, "NYPD. We're looking for Michael Stofferson." There was no answer but they could hear a TV on in the background. "Sir, we know someone's in there. We just need to ask you a couple questions." Still no response.

"Did you hear someone ask for help?" Dean asked and Sam nodded. Before Beckett could respond Dean had moved to the door and was kicking it in yelling, "FB...I?" They all looked into the room, even Castle, as they stared at the contents of the room.

"Well this is a first," the author said.


	4. AN: On Hiatus

**I really hate to say this, considering I know a lot of people want to see this continue, but 'Biting the Big Apple' is going on full-time hiatus. I don't know when I'll get back to it but I have lost all desire to work on this story. That tune may change once new Castles and/or Supernaturals start up but I can't guarantee it. That being said I _do_ plan to finish this as I hate leaving things unfinished.**

**The problem so far has been the meat of the story. I know how I want the final scenes to go but I can't settle on how to get there. I'll do my best to keep people posted but until then please check out some of the other Castle and/or Supernatural stuff on here. 'SisterDramamine' has a great set of Supernatural AUs I'd recommend. Until later, happy reading!**

**DragonKnight159**


End file.
